Coarctation of the aorta (CoA) is associated with decreased exercise capacity despite successful repair. Altered flow patterns have been identified due to abnormal aortic arch geometry. Our previous work demonstrated aorta size mismatch to be associated with exercise intolerance in this population. In this study, we studied aortic flow patterns during simulations of exercise in repaired CoA using 4D flow cardiovascular magnetic resonance (CMR) using aortic replicas connected to an in vitro flow pump and correlated findings with exercise stress test results to identify biomarkers of exercise intolerance. Patients with CoA repair were retrospectively analyzed after CMR and exercise stress test. Each aorta was manually segmented and 3D printed. Pressure gradient measurements from ascending aorta (AAo) to descending aorta (DAo) and 4D flow CMR were performed during simulations of rest and exercise using a mock circulatory flow loop. Changes in wall shear stress (WSS) and secondary flow formation (vorticity and helicity) from rest to exercise were quantified, as well as estimated DAo Reynolds number. Parameters were correlated with percent predicted peak oxygen consumption (VO2max) and aorta size mismatch (DAAo/DDAo). Fifteen patients were identified (VO2max 47 to 126% predicted). Pressure gradient did not correlate with VO2max at rest or exercise. VO2max correlated positively with the change in peak vorticity (R = 0.55, p = 0.03), peak helicity (R = 0.54, p = 0.04), peak WSS in the AAo (R = 0.68, p = 0.005) and negatively with peak WSS in the DAo (R = − 0.57, p = 0.03) from rest to exercise. DAAo/DDAo correlated strongly with change in vorticity (R = − 0.38, p = 0.01), helicity (R = − 0.66, p = 0.007), and WSS in the AAo (R = − 0.73, p = 0.002) and DAo (R = 0.58, p = 0.02). Estimated DAo Reynolds number negatively correlated with VO2max for exercise (R = − 0.59, p = 0.02), but not rest (R = − 0.28, p = 0.31). Visualization of streamline patterns demonstrated more secondary flow formation in aortic arches with better exercise capacity, larger DAo, and lower Reynolds number. There are important associations between secondary flow characteristics and exercise capacity in repaired CoA that are not captured by traditional pressure gradient, likely due to increased turbulence and inefficient flow. These 4D flow CMR parameters are a target of investigation to identify optimal aortic arch geometry and improve long term clinical outcomes after CoA repair.

中文翻译：

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4D 血流心血管磁共振改变的血流动力学可预测主动脉缩窄修复后的运动不耐受：一项体外研究


尽管修复成功，主动脉缩窄 (CoA) 仍与运动能力下降相关。由于主动脉弓几何形状异常，已发现血流模式发生改变。我们之前的工作表明，主动脉尺寸不匹配与该人群的运动不耐受有关。在这项研究中，我们使用连接到体外流量泵的主动脉复制品，使用 4D 血流心血管磁共振 (CMR) 模拟修复 CoA 的运动过程中的主动脉血流模式，并将结果与​​运动压力测试结果相关联，以识别运动不耐受的生物标志物。在 CMR 和运动负荷测试后对 CoA 修复患者进行回顾性分析。每个主动脉均经过手动分割和 3D 打印。在使用模拟循环血流回路模拟休息和运动期间，进行了从升主动脉 (AAo) 到降主动脉 (DAo) 的压力梯度测量和 4D 血流 CMR。量化从静止到运动的壁面剪应力 (WSS) 和二次流形成（涡度和螺旋度）的变化，以及估计的 DAo 雷诺数。参数与预测峰值耗氧量百分比 (VO2max) 和主动脉尺寸不匹配 (DAAo/DDAo) 相关。确定了 15 名患者（预计最大摄氧量 47% 至 126%）。压力梯度与休息或运动时的最大摄氧量无关。 VO2max 与峰值涡度 (R = 0.55, p = 0.03)、峰值螺旋度 (R = 0.54, p = 0.04)、AAo 中峰值 WSS (R = 0.68, p = 0.005) 的变化呈正相关，与峰值 WSS 呈负相关从休息到运动的 DAo (R = − 0.57, p = 0.03)。 DAAo/DDAo 与 AAo 中的涡度 (R = − 0.38, p = 0.01)、螺旋度 (R = − 0.66, p = 0.007) 和 WSS (R = − 0.73, p = 0.002) 和 DAo ( R = 0.58，p = 0.02）。 估计的 DAo 雷诺数与运动时的最大摄氧量 (R = − 0.59，p = 0.02) 负相关，但与休息时的 VO2max 不相关 (R = − 0.28，p = 0.31)。流线型图的可视化表明，主动脉弓内有更多的二次血流形成，具有更好的运动能力、更大的 DAo 和更低的雷诺数。修复后的 CoA 的二次流动特征和运动能力之间存在重要的关联，而传统的压力梯度无法捕获这些关联，这可能是由于湍流增加和流动效率低下所致。这些 4D 血流 CMR 参数是确定最佳主动脉弓几何形状并改善 CoA 修复后长期临床结果的研究目标。